The present invention relates generally to a slip-type apparatus for gripping and manipulating tubular members, such as drill pipe and bottom-hole assembly components. More specifically, the present invention relates to an automated apparatus for manipulating pipe members into and out of petroleum wells.
A typical slip-type apparatus generally comprises a plurality of circumferentially spaced slip bodies that can be placed around the locus of a drill pipe or other tubular member. The inner sides of the slip bodies carry gripping members, usually in the form of teeth, for frictionally engaging the drill pipe or tubular member. The outer sides of the slip bodies generally have tapered surfaces that are inclined inwardly from top to bottom.
In a typical well drilling operation, the slip-type apparatus is secured around the pipe member and placed in the portion of the rotary table referred to as the rotary table bushing or “bowl.” Because the slip bodies can move both longitudinally and radially with respect to the bowl, these inclined surfaces serve as camming surfaces. Thus, when the weight of the pipe member is set down on the slip-type apparatus, so that it tends to move the slip bodies downwardly with respect to the bowl, the camming surfaces urge the slip bodies radially inwardly and into tighter engagement with the pipe member. Once set, the slips will support the weight of the drill pipe and/or other tubular members suspended therefrom.
In the past, such slip-type devices were manipulated manually by individuals working on the rig floor referred to as “roughnecks.” The operation of securing the slip-type apparatus around the pipe member and in and out of the bowl presented a certain degree of danger to the roughnecks—accidents were commonplace. To alleviate this dangerous situation, automated “slip pullers” were developed. These devices essentially secured the slip-type device around the pipe member and in and out of the bowl without direct human intervention. While an improvement over the manual process, the automated slip puller did not eliminate risk entirely.
The automated slip pullers of the prior art were designed such that the devices were secured over the rotary table—usually via the drive or “kelly” bushings. Due to the unique operation of the prior art devices, the body of the slip pullers extended beyond the boundaries of the rotary table below. Such a prior art device is demonstrated, in FIGS. 1(a-c).
This design presented a potentially dangerous situation. If the rotary table began to spin with the automated slip puller attached, that portion of the device that extended beyond the boundary of the rotary table would spin as well, causing damage to any equipment, or injury to any individual, near the area. The present invention eliminates this potentially dangerous situation.